Fatty15 contains a single active ingredient: pentadecanoic acid, also known as C15:0, a type of odd-chain saturated fatty acid. Each capsule delivers 100 mg of this fat, and the recommended dose is one capsule per day. That simplicity is the product’s main selling point: one ingredient, one capsule, no complex formulations.
What C15:0 Actually Is
Pentadecanoic acid is a 15-carbon saturated fat found naturally in whole dairy products like butter and full-fat milk. It belongs to a category called odd-chain saturated fatty acids, which are structurally different from the more common even-chain fats (like the 16-carbon palmitic acid found in palm oil). Your body doesn’t produce C15:0 on its own, and as diets have shifted away from whole-fat dairy over the past several decades, blood levels of this fat have declined in many populations.
The version used in Fatty15 is a pure, free fatty acid form of C15:0. It has been evaluated by the Flavor and Extract Manufacturers Association (FEMA) expert panel and carries a GRAS (Generally Recognized as Safe) designation on the FDA’s food substances database, where it is listed as a flavoring agent.
How C15:0 Works in the Body
C15:0 does two main things at the cellular level: it strengthens cell membranes and supports mitochondria, the structures inside cells that produce energy.
Because C15:0 is a saturated fat with an odd-numbered carbon chain, it resists the kind of damage (called lipid peroxidation) that breaks down cell membranes over time. When it integrates into cell membranes, it makes them more stable and less vulnerable to oxidative stress. Research published in the World Journal of Cardiology found that supplementation with C15:0 improved red blood cell stability and reduced the breakdown of red blood cells in animal studies.
On the mitochondrial side, C15:0 at concentrations around 10 to 50 micromoles per liter restores the electrical charge that mitochondria need to generate energy efficiently. Specifically, it boosts the activity of a key step in the energy production chain (complex II), which helps cells produce more of their primary fuel, ATP, while generating fewer harmful byproducts called reactive oxygen species. In simpler terms, it helps your cells’ power plants run more cleanly. It also activates pathways involved in creating new mitochondria, which could increase the overall supply of healthy, functioning energy producers in tissues like the heart.
What the Research Shows
The most relevant human trial to date tested C15:0 supplementation in young adults with overweight and obesity. Among participants whose blood levels of C15:0 rose above a threshold of 5 micrograms per milliliter, liver enzyme levels dropped significantly. One key liver enzyme (ALT) decreased by 29 units per liter, and another (AST) dropped by 6 units per liter, compared to participants who didn’t reach that blood level. Elevated liver enzymes are a common marker of liver stress, so these reductions suggest a meaningful effect on liver health, though only in people who absorbed enough of the supplement to cross that concentration threshold.
Notably, only about half the participants in the treatment group actually reached the effective blood level. This suggests individual absorption can vary, which is worth knowing if you’re considering the supplement. The researchers identified 5 micrograms per milliliter (roughly 20 micromoles per liter) as the concentration where C15:0 appears to become biologically active, both in cell studies and in animal models.
Animal research has shown additional effects. In a mouse model of fatty liver disease, C15:0 treatment significantly reduced lipid peroxidation in the liver. In dolphin studies (the animals where C15:0 deficiency was first identified), raising red blood cell membrane C15:0 from 0.17% to 0.58% of total fatty acids stabilized red blood cells and resolved anemia.
What a Threshold Blood Level Means for You
Researchers have proposed that cell membranes need C15:0 to make up more than 0.4% to 0.64% of their total fatty acids for optimal long-term health. Below that range, membranes become more fragile and mitochondria more prone to dysfunction. This framing positions C15:0 not as a therapeutic drug but as a nutrient your cells need a minimum amount of to function well, similar to how you need a baseline level of vitamin D or omega-3 fatty acids.
Whether the 100 mg daily dose in Fatty15 reliably gets most people above that threshold is still an open question. The clinical trial showed that roughly half of supplemented participants crossed the key blood concentration, meaning the other half did not. Factors like diet, body composition, and individual metabolism likely play a role.
How to Take It
The manufacturer recommends one capsule daily, taken with or without food. Since the supplement’s near-term effects peak about four to six hours after taking it, most users take it in the morning. Some prefer taking it in the evening, reporting it supports their sleep. There are no specific instructions about pairing it with fat-containing meals, which is notable since many fat-soluble supplements absorb better with food.
The capsule itself is small and straightforward. Fatty15 does not contain a blend of multiple ingredients, vitamins, or herbal extracts. What you’re getting is a measured dose of a single fatty acid, which makes it easy to evaluate on its own merits without untangling the effects of a complex formula.